Turbo and HP relation. Am I wrong here??

[woolveren]

Hi,

This may be a dumbest question from my side. But just wanted to make sure whether I got it it in the right sense or not...

If a turbo car (for example the B5 A4 1.8T) specs says that the Horse Power is 150 @5700 RPM, does this value indicates the final amount of the horse power we get when the Turbo is active? (This is what I actually thought till this time..)

The reason why I am asking this is because today one of my co-worker said that the turbo increases HP by some percentage(which I already know) and if your car spec says 150 Hp, then the final amount of HP it produces is 150 + Some percentage.

Say for example, 150 + 20% = 180 HP.

Is this true?

[Stubek]

adding a turbo to a car that does not have one might get you around a 20% gain, but the numbers from the factory are for when the turbo is active, so your example here, the power is 150, not 150 + x%.

[woolveren]

adding a turbo to a car that does not have one might get you around a 20% gain, but the numbers from the factory are for when the turbo is active, so your example here, the power is 150, not 150 + x%.

Yeah, that's what my understanding too..

He drives a nissan altima and I think he has some plans to put a turbo on it.

Thanks for the clarification..

[Seerlah]

If you didn't have your turbo, your car would likely put out around 90bhp. When your turbo is having issues, you are not seeing 150bhp. And that 150bhp is for a fresh engine. Your engine stock is likely putting out less power. And as well all know these cars are slow, but damn fun to drive.

[Max@034]

Hi,

This may be a dumbest question from my side. But just wanted to make sure whether I got it it in the right sense or not...

If a turbo car (for example the B5 A4 1.8T) specs says that the Horse Power is 150 @5700 RPM, does this value indicates the final amount of the horse power we get when the Turbo is active? (This is what I actually thought till this time..)

The reason why I am asking this is because today one of my co-worker said that the turbo increases HP by some percentage(which I already know) and if your car spec says 150 Hp, then the final amount of HP it produces is 150 + Some percentage.

Say for example, 150 + 20% = 180 HP.

Is this true?

Motors do not create their peak horsepower through the whole rev range. Depending on their displacement, design, cylinder number, etc, will all affect where the car reaches its peak horsepower, which is a direct relation of torque and rpm. When a car says 150bhp @ 5700rpm, that means the absolute highest point of the curve is at 5700rpm. So at 5000rpm, you have less then 150bhp, and at 6500rpm, you have less then 150bhp.

You can have one car that produces 150bhp @ 5700rpm, and another car that produces 150bhp @ 5700rpm, and they could be WORLDS different since what matters is the power UNDER the curve; ie when the power comes in, is there torque, do you have to rev the engine all the way to redline etc.

Turbos work based on exhaust gases spinning a turbine which in turn spins a compressor wheel and "forces" extra air through the motor. Motors are just about bringing in air and gasoline, mixing it, combusting it, and expelling it.

A turbo will never give some "specific" percentage of power to a car. Turbos come in almost an infinite amount of combinations of housing sizes, wheel sizes, AR's, everything which change the way the power is delivered to a car. You could strap on a big turbo onto your car and it may actually be slower, despite you putting down more "peak" power (ie if you put too large of a turbo and it won't spool until redline, leaving the whole bottom of your curve dead, where you spend 90% of your time).

Turbos are used to add low powerband or mid powerband or high end powerband, it all depends on the turbo used. A small turbo will spool and respond faster, producing power earlier, but running out of breath up high. Your factory K03 turbo is a perfect example of this, as you'll notice if you race a bigger turbo car, you will pull ahead for a second while the larger turbo spools. People chose their turbos based on what they want out of a car; Volkswagen chose the K03 cause it responds quick and almost everyone drives their cars in the low RPM.

Just don't get confused into thinking there is some simple linear correlation between the amount of power you get and the sized turbo you put on. Your motor is only so big.

[M-Hood]

Very simple answer, HP ratings are at WOT. LOL

[Avant Nate]

Horespower is primarily just a function of X amount of air + Y amount of fuel. Two ways to increase power, more displacement or more air. All turbos do is force more air into a combustion chamber. On a NA car adding a turbo can seem like a percentage, because if you add 20% more air=20% more power. Now this is a really simplified explanation and alot of other factors come into play. The reason its easy to add hp to a turbo car is just add more air.